Method of making clutch plate



s. K. WELLMAN 2,799,603

METHOD OF MAKING qLu-rcn PLATE 9, 1947 JuI 16, 1957 3 Sheets-Sheet 1Original Filed Aug.

1957 s. K. WELLMAN 2,799,603

METHOD OF MAKING CLUTCH PLATE Original Filed Aug. 9, 1947 a Sheets-Sheet2 INVENTOR 5AM UEI. ILWELLMA/ July 16, 1957 s. K. WELLMAN METHOD OFMAKING CLUTCH PLATE Original Filed Aug. 9, 1947 'IIIIIIIIII m QR INVENTO621M051. Kh L'ZL United States Patent 2,799,603 METHOD OF MAKING CLUTCHPLATE 1947, Serial No. 767,706, dated July 21, 1953. Di-

14, 1953, Serial No.

Original application August 9,

now Patent No. 2,646,151, vided and this application July 367,876

2 Claims. (Cl. 148-12.4)

This application is a division of co-pending application Serial No.767,706 (now Patent No. 2,646,151), and relates to an improved method ofmaking a clutch plate for use in motor vehicles and similar mechanismswherein the clutch plate is disposed between two parts of a drivingmember, such as a pressure plate and a flywheel, and is adapted to beclamped therebetween in order to transmit power from the flywheel to theclutch plate. The invention relates particularly to a cushion clutchplate of the all-metal type which utilizes sintered metal frictionfacing material.

It is an object of the present invention to provide a new and improvedmethod of making a cushioned clutch plate.

Other and further objects will appear ing description in which:

- Fig. 1 represents a front elevation of the improved cushion clutchplate;

Fig. 2 is a section on line 2-2 of Fig. 1 and on an enlarged scale;

Fig. 3 shows a portion of the clutch plate of Fig. l on an enlargedscale;

Fig. 4 is a diagrammatic sectional showing of the periphery of the plateand on an enlarged scale;

Fig. 5 is a view corresponding to Fig. 4 but with the plate incompressed condition;

Fig. 6 is a plan view of a forming ring for forming the curve in theperiphery of the plate;

Fig. 7 is a section on line 7-7 of Fig. 6 and on an enlarged scale;

Fig. 8 is an exploded view of the furnace fixture for forming the clutchplate to sinuous shape;

Fig. 9 is a diagrammatic vertical section on an enlarged scale of thefurnace fixture of Fig. 8, but showing the same in a compressedcondition; and,

Fig. 10 is a view similar to-Fig. 9 but illustrating a modification.

It is a recognized fact that clutch plates, particularly those for usein passenger cars, should provide some cushioning action both during theengagement operation and also during the driving operation. Thiscushioning action is desirable in Order to obtain a smooth transmissionof power during the engagement between driving and driven members aswell as to provide a limited amount of cushioning action to absorbvibrations and to accommodate slight misalignments of the driving anddriven members. Accordingly, clutch plates have been constructed ofmultipart construction and using springs to provide the desiredcushioning action. For vibrational and torsional cushioning, it iscommon to make the plate in two or more parts as by separating the hubfrom the friction carrying periphery and join these parts with springs.Similarly, it has been customary to slot the periphery of the plate inthe thought that this would provide a certain amount of resilience orcushioning action during the engagement of the plate. None of theseexpedients have been found to be entirely satisfactory in that themultipart constructionincreases the weight of from the followthe clutchplate with a resultant increase in its inertia and greater difliculty inshifting gears. The slotting of the periphery of the plate weakens thesame and either results in failure by fracturing of the plate as betweenslots 01' in chattering of the plate during engagement.

The conventional clutch plate is provided With friction facings made ofnon-metallic materials usually asbestos and other ingredients in a resinor rubber base binder. These materials are not entirely satisfactory inthat they are affected by heat, pressure, temperature, and liquids, suchas oil and water. It is common knowledge that overheating of theseplates as sometimes occurs in service has resulted in softening of thebinder and destruction of the friction facings.

An improved type of friction material is that known as sintered metalfriction material. This material is made by pressing and sintering apredominantly metallic mixture of metallic and non-metallic powders. Theresultant product is a metallic appearing structure comprising a porousmetallic network having soft metals such as lead and non-metallic suchas graphite and silica disposed in the pores thereof. These sinteredmetal friction materials are not so subject to being affected byvariations in operating conditions and are, of course, not chemicallychanged by contact with liquids such as oil. In certain installations,these sintered metal friction materials have been found more suitablethan the conventional non-metallic material. However, due to theirmetallic character, they are heavier and less compressible thannon-metallic materials. Their added weight has practically preventedtheir use in passenger automobiles. A further factor which has limitedtheir use has been their great wear resistance in that they must beinstalled with great care to insure satisfactory operation. Due to thisrelatively little wear, the materials will not seat themselves orreadily wear-in when improperly installed. It has been previously almostimpossible to overcome these objections.

If the new sintered metal friction material is substituted in aconventional clutch plate having a multipart construc tion andcompression springs, the great weight of the resultant clutch plate willprevent its use in most installations. Similarly, the incompressiblenature of the material has rendered the use of peripheral slotsinadequate for cushioning action and the slots make it difiicult toinsure that the plate and the friction segments are fiat and in properalignment. Attempts have been made to directly bond the sintered metalfriction material to the carrier plate of a clutch plate. These attemptsare not very satisfactory in that the heat of the bonding operation sosoftens or anneals the plate as to seriously reduce its strength. Thus,although a plate of slightly less weight was obtained, the plate was notsatisfactory in service.

It is essential that a clutch plate be of adequate strength to withstandthe stresses it receives in service. If the plate is made thick enoughto avoid distortion, it is generally too heavy for use. One suggestedsolution is to utilize a thin coned or dish shaped plate. These have notbeen too satisfactory and cannot be used with sintered metal facingmaterial and obtain satisfactory results. The sintered metal facingmaterial, being metallic, conducts heat from the friction surface intothe coned plate. Any repeated heating and cooling of a coned or dishedplate quickly results in distortion and warping of the same due to theexpansion of the metal thereof.

Applicant has developed a new and improved method for making a clutchplate which utilizes sintered metallic friction material and providesrequisite cushioning action during engagement and torsional resilienceto absorb vibrations and accommodate shaft misalignments. The inventionrelates particularly to a cushioned clutch plate of the all-metal typewhich is fiat and which comprises a flat center portion carrying a huband a peripheral portion joined to the hub by spaced spokes. Frictionsegments are secured to the peripheral portion in a spaced and staggeredmanner and the whole is constructed so that the requisite cushioningaction is provided without excessive Weight. The invention will be moreclearly understood by reference to the following description.

Fig. 1 shows a clutch plate constructed in accordance with the inventionand comprising a carrier plate 1 secured at the center thereof to aflanged hub 2 by means of rivets 3 extending through rivet holes 5 inthe carrier plate 1. As shown in Fig. 2, the hub 2 is provided with acentral splined opening 4 for reception of the usual splined shaft. Thehub 2 fits in a hole of the plate and is provided with a flange 6 havinga shoulder 7 against which the center portion 8 of the carrier plate 1fits and to which it is secured by means of the rivets 3.

The center portion 8 of the carrier plate 1 which abuts the flange 6 ofthe hub 2 is flat as shown in Fig. 2 and is secured to the peripheralportion 9 of the carrier plate 1 by means of the spokes 11 which are ofgenerally spiral shape. As shown in the enlarged view of Fig. 3, thespokes 11 are formed by the cut-outs or slots 12. These slots are ofgradually increasing width in a radially outward direction thus causingthe spokes to be of a decreasing width outwardly. The ends of the slots12 are provided with smoothly rounded corners 13 so as to avoid theformation of sharp corners and the resultant localization of stresses.

As will be seen from Fig. 3, the peripheral portion 9 of the carrierplate 1 is of wave shape and is formed of a plurality of flat triangularportions or areas 22 joined by spring portions 20 so as to form asinuous or somewhat wave-like shape in a circumferential direction. Theflat portions or areas 22 form flattened crests on the waves. The springportions 20 are of smoothly curved form and comprise spring sectionsjoining the flat triangular POT. tions 22. As shown in Figs. 1 and 3,these flat triangular portions or areas 22 are located at the center ofthe friction segments and extend radially across the pe ripheral portion9 of the clutch plate.

Friction pads or segments 14 are secured to the peripheral portion 9 ofthe plate in spaced relation, each pad being secured at its center tothe top ofa triangular portion and in alternate arrangement on oppositesides of the plate. In the arrangement shown in Fig. 1, it will beobserved that there are six segments secured to each side of the plateand that the segments on one side are in staggered relation with respectto the segments on the other side of the plate. It is further shown inFig. 1 that since staggered segments 14 are used, there must always bean even number of segments; therefore there must also always be an evennumber of spokes 11. In addition, the segments overlap in a peripheraldirection.

The arrangement of the segments on the curved periphery 9 of the platecan be more easily understood from reference to Figs. 4 and 5. It willbe seen that each segment 14 comprises a steel backing member 16 havingintegrally bonded thereto a sintered metal facing material 17constructed in a manner described hereinafter. The curved peripheralportion 9 of the carrier plate is formed of flat portions 22 (thetriangular areas) joined by spring portions 20 as described above andthe friction segments 14 are secured thereto at the Hat portions bywelding as indicated at 18. Preferably, projection welding is utilized.In this type of welding, the peripheral portion 9 of the plate isprovided with a small projection or raised portion at the spot where itis desired to secure the segment. The segment 14 is then placed on thisprojection and electrodes placed on the opposite sides of the segment 14and plate 1. When a suitable electric current is passed between theelectrodes, the projection localizes the passage of current, fuses andforms a strong weld. As is shown in Fig. l, we have illustrated the useof two projection welding points 18 for each segment, but it is Iimportance.

apparent that this may be modified and other attaching means, such asrivets, could be used.

The form of the peripheral portion of the plate is of Fig. 4diagrammatically shows the plate in uncompressed condition while Fig. 5shows it in the position it assumes when fully compressed between thepressure plate and the flywheel of a motor vehicle. It will be seen thatthe spring portions 20 of the plate have been flattened during thecompression. The overlapping portions 19, see Fig. 5, of the segments 14prevent distortion of the peripheral portion beyond the flattenedposition. It will be understood that Fig. 5 is diagrammatic. The showingin this figure assumes that the peripheral portion of the carrier platehas been straightened. It represents the results if a rectangular stripof steel were being used.

The peripheral portion 9 of the plate will not be stressed beyond itselastic limit because there is no sharp bend during the compressingoperation. The compressing step merely gradually flattens the peripheralportion. There is some compression of the steel during this, but ofnegligible amount. The length of the peripheral portion between adjacentedges of adjacent triangular areas of the segments shown in Fig. 4 formsa spring portion 20. It will be noticed that this spring portion is ofconstantly decreasing length as the plate is depressed and flattened.This constantly decreasing length of the spring results in a constantlyincreasing strength of the spring. In other words, the force required tocompress the spring increases greatly as the spring is compressed.

The spokes 11 are so arranged as to minimize undue flexing during thecompression of the plate. In Figs. 3, 4, and 5, the dotted line 21designates the neutral plane of the spoke 11 and the attached springsection 20. Theoretically, the peripheral portion 9 of the plate at thispoint does not move during compression. In compression, the portion ofthe spring 20 to the left of this dotted line is bent down (Fig. 4) andthe portion to the right spokes 11 of the plate, they connect to theperipheral portion of the plate in the neutral plane or line 21 of eachspring portion 20 as is evident from Fig. 3. As a result of this,although the plate may be compressed repeatedly, the spokes are notsubject to flexing or distortion to any appreciable extent and will notfail due to fatigue. They are, however, free to flex to cushionvibration and accommodate misalignment between driving and drivenmembers. Their attachment to the peripheral portion at the neutral planeserves to greatly reduce the amount of flexing to which they aresubjected and minimizes V fatigue problems.

The spokes 11 are of generally spiral shape in order to obtain greatlength. The use of a spiral spoke of this type permits a spoke lengthapproximately twice that which would be obtained if a radial spoke wereused. This greater length of the spokes 11 permits a spoke of greatercross-section and increased strength to be used while at the same timeretaining the resilient construction. If radial spokes were used, thegreatly reduced length thereof would necessitate the use of very narrowspokes in order to obtain the same degree of spring action in the plate.Such small spokes would be much more subject to failure in service.

Another important feature of the improved clutch plate is that thespring pressure or force required to compress the plate is substantiallyuniform over the face of each segment. As will be observed from Figs. 1and 3, the segments 14 contact the curved peripheral portion 9 on a flattriangular area 22. The adjacent edges 23 and 24 of the adjacenttriangular areas are parallel as shown in Fig. 3. Thus, the distance 26between parallel lines represents the spring portion 20 shown in Figs. 4and 5. Since this spring portion has the same length at its outerperiphery as at its inner periphery, it is apparent that the pressurerequired to compress the spring portion will be uniform over thesegments 14, since the steel backing 16 thereof is sufficiently strongand stiif to resist bending.

The spokes 11 serve to give torsional resilience to the 7 plate andfunction in the same manner as the usual helical compression springsused in multipart clutch plates to absorb vibration and to permit alimited amount of axial misalignment between the driving and drivenmembers.

As one example, I have constructed the clutch plate shown in Fig. 1 withan outside diameter of 9 inches and a peripheral portion 9 having aradial width of about 1% inches. The segments 14 had an outsideperipheral chord length of 2% inches. The carrier plate 1 was made ofSAE 1035 steel of a thickness of .070 inch and hardened and drawn to aRockwell C hardness of 20-25. The segments 14 had a steel backing of SAE1010 composition and a thickness of .062 inch and a facing inchthick ofa composition described below. The spring portions 20 of the peripheralportion 9 of the plate had a length of about 1 /2 inches and acompressive height of .040 inch. A force of 1500 pounds was required tofully compress this plate.

Generally, the clutch plate 1 should be installed so that the directionof rotation of the plate is such that the spokes 11 are placed intension when a driving force is applied. However, opinions differ as towhether the spokes should be in tension or compression duringacceleration. Where the clutch plate is used in heavy trucks in hillylocations where the engine is used for braking the truck on steepgrades, it has been suggested that the plate should be installed so thatthe spokes are in tension during this deceleration or braking action.

The method of constructing a clutch plate, such as that shown in Fig. 1,comprises the assembly of the various parts. As has been described theclutch plate comprises a hub 2, a carrier plate 1, and twelve frictionsegments 14 (in the modification shown). The hub 2 is of conventionalconstruction and is generally made by machining a steel forging. Thecarrier plate 1 is formed by stamping a flat plate from a sheet or stripof steel of suitable composition and thickness. I have found itpreferable to use SAE 1035 steel. This should be of coldrolled typesince thickness variations are small with steel of that type. The plateis formed to the desired shape and configuration in a manner to bedescribed hereinafter. The friction segments 14 are also produced in amanner to be described later. The carrier plate 1 is secured to the hub2 by means of rivets 3 and friction segments 14 are then secured to theperipheral portions 9 of the carrier plate 1 by means of projectionwelding as described above or some other method. The resulting plate isthen balanced and is ready for use. In some cases it may be necessary togrind the friction surfaces of the friction segments 14 to insureaccurate alignment.

The formation of the curved carrier plate of Figs. 1 through 5 issomewhat involved. This plate should be heated, quenched andstress-relieved in order to achieve the proper characteristics. Thismust be done in a manner which will insure accurate formation of thecurved periphery.

The carrier plate of Fig. 1 may be formed by stamping from flat steel ofsuitable thickness and composition, a plate of the general form shown inFig. 1 having slots 12, rivet holes 5 and a central cut-out forreception of the hub. After the plate has been stamped to shape, itshould be hardened by heating to a temperature above the critical pointand quenched in oil or other suitable medium while clamped in a fixturethat will form the convolutions or bends in the peripheral portion ofthe plate. A temperature of about 1550 F. is satisfactory. Quenchingfixtures are common and are frequently used for the quenching to shapeof springs of various shapes and it has not been deemed necessary toshow this apparatus.

The resultant curved plates will not be of uniform curve. In otherwords, the peripheral portion of each plate will not have exactlyuniform shape nor will the curves of successive plates correspond due tothe inherent diflicultiesof controlling the clamping operation and theflow of cooling fluid. It is essential that these curves be uniform notonly to secure uniform compressible action but to insure that thefriction segments 14 when secured to the plate will have their outersurfaces in the same plane on each side of the plate and that the faceson one side will be parallel to the faces on the other side. It will bereadily appreciated that since these segments are relatively long andare secured only at their centers, a slight tilting of the Hattriangular area 22 of the peripheral portion of the plate will result ina considerable elevation of the end of the segment above the desiredplane. A clutch plate in which the outer faces of the segments are notin the same plane and which has raised corners on the segments willchatter and vibrate in use and will not be satisfactory. To achieveuniform curving of the peripheral portion of the plate, I have devisedthe expedient of drawing the hardened plate in the special fixture shownin Figs. 6 through 8.

After the plate has been heated and quenched in oil to harden the same,it is curved to the general shape desired but is in a hard and stressedcondition. It is desirable to heat the plate to a drawing or stressrelieving temperature before placing it in use. I propose to utilizethis drawing operation to finally form the desired convolutions in theperiphery of the plate. This is accomplished by use of forming rings 35such as shown in Fig. 6 and the fixture 40 of Fig. 8. The ring 35comprises a peripheral portion 36 having three spaced holes 37 andtwelve triangular members or portions 38. The inside diameter 39 of theperipheral portion 36 of the ring is slightly greater than the outsidediameter of the carrier plate 1. The triangular segments 38 are soshaped and arranged as to correspond with the triangular portions 22 inthe peripheral portion of the plate.

A plurality of forming rings 35 and carrier plates 1 are assembled onthe fixture 40 shown in Fig. 8 which comprises a thick cast iron baseplate 41 having three vertical pins 42 spaced about the outer peripherythereof for guiding the forming rings 35 by extending through the holes37 and three vertical spaced pins 43 located at the inner peripherythereof for guiding the carrier plates by extending through the rivetholes 5. For clarity, only one pin 42 and one pin 43 are shown. Thesepins extend upwardly and are adapted to be received in holes 50 in anupper cast iron plate 44. Downward movement of plate 44 forces anassembly of carrier plates and forming rings against the lower plate.The upper plate 44 is in turn provided with three spaced pins 45 andthree spaced pins 46 for reception of carrier plates and forming rings.A still further cast iron plate 48 is provided for placement on the pins45 and 46. It will be readily seen that although only two complete unitscomprising three plates are shown, a plurality of units may besuperimposed. The completed stack of assembled units is adapted to beplaced in a furnace, held under pressure, and heated to a temperaturesufiicient to relieve the stresses in the carrier plates and to formthem to the desired shape. I have found it preferable to use a furnacesuch as that shown in Wellman Patent No. 2,258,431, issued October 7,1941, but any furnace can be used which is adapted to hold the assembledstack under pressure while heating the same.

In order to properly form the carrier plates, they are assembled withthe forming rings generally shown at 35 in Fig. 6. It will be seen thatthe carrier plates 1 are of slightly less diameter than the spacebetween the pins 42 and that the rivet holes 5 in the carrier platesreceive the pins 43. Holes 37 in the forming rings 35 receive the pins42. The pins 42 and 43 are so located that the triangular portions 38 ofthe forming rings 35 are accurately aligned with the desired triangularportions 22 of the carrier plates 1.

Since the central portion 8 of the carrier plate is flat, it isnecessary to provide flat spaced rings or washers'to maintain the samein flat condition. These are shown in Fig. 8 at 47. In order to achieveinclined spring portions having a height such as to permit a compressionof .040 inch, the forming rings 35 and washers 47 should have athickness of .040 inch. However, the bottom and top washers 51 mustobviously have a thickness of half this or .020 inch due to the flat andparallel faces of the cast iron plates 41 and 44. Similarly, the bottomand top forming ring 49 should have only six instead of twelvetriangular portions. The top ring should have its triangular portionsoffset by from those of the bottom ring.

The arrangement and operation of the forming rings and the fixture 40can best be understood by reference tothe schematic showing of Fig. 9.This figure shows a plurality of carrier plates 1 clamped between theheavy cast iron plates 41 and 44. This view shows a section of theperiphery of the carrier plates in a manner similar to that of Figs. 4through 5. As in those figures, the diagrammatic showing is made in amanner to best illustrate the curved nature of the periphery and theshowing is somewhat similar to that obtained if a series of straightplates were used rather than peripheral portions of a circular object.it will be noticed that the peripheral portions of the carrier plates 1have been formed to curved shape comprising flat areas 22 joined byinclined spring portions 20. This curvature is obtained by use of thetriangular portions 38 which are disposed between the carrier plates 1in such a manner that compression between parallel cast iron plates 41and 44 results in bending of the carrier plates. It will be seen thatportions 38 of the same forming ring 35 are distorted by this action. Itwill be also noted that the triangular portions 38' of the top formingring 49 and the triangular portions .38" of the lower forming ring 49are offset 30 and that the bottom and top forming rings use only six orone-half as many triangular portions as the central forming rings.

After the forming rings, washers, and carrier plates are assembledbetween the cast iron plates 41, 44, and 48, the assembled unit isplaced in a furnace such as that described above and heated to asuificient temperature to relieve stresses in the carrier plates andform the peripheral portions to the desired contour. I have found itpreferable in treating a carrier plate constructed as described above topress the assembly under a pressure of 100 pounds per square inch andheat the same to a temperature of about 1000 F. and then allow theassembly to cool in the furnace.

The carrier plates when removed from the furnace after the abovetreatment have accurately formed peripheral portions and center portionsthat are flat and in alignment. The plate itself should have a hardnessof Rockwell C 20-25.

While I have described the use of SAE 1035 steel for the carrier plateand the formation of the wave shape in the periphery as being first donein a hardening step followed by a drawing step, it is clear that othersteels can be used and that the process may be varied. For example, asteel of higher carbon content such as SAE 1070 steel may be used. Thissteel, if in cold rolled condition, is sufiiciently strong so that nohardening is necessary for some applications. In that case, the heatingand quenching steps are omitted and the periphery is formed merelythrough use of the forming apparatus shown in Figs. 6 to A heating stepusing this apparatus in the manner previously described results in theformation of the Waves as well as the relieving of any stresses in theplate such as those caused by the operation of stamping the plate from asheet of steel. The heating and forming step is accomplished at atemperature not sufiiciently high to reduce the strength of the platebelowacceptable limits.

After the carrier plate is properly formed, it is secured to themachined hub 2 by means of the rivets 3,

I These backing members are cleaned and then provided with athinplating-of a protective metal, such as copper or nickel. Thefriction facing material 17 is prepared by pressing to desired shape asuitable mixture of metallic and non-metallic powders to form a flatbriquette. This briquette is then placed on the plated backing member 16and pressed against the same under a pressure of approximately poundsper square inch while being heated to a sufficient temperature to sinterthe facing material and cause it to integrally bond to the steel backingmember. As one example, I have used a facing material comprising:

Percent by weight 67.26 5.31

Graphite c Silica This mixture is pressed under a pressure of 11 tonsper square inch to form the briquette. It is sintered at a temperatureof approximately 1450 F.

The segments 14 can be made to the desired shape or they may be cut fromalarger piece of material. It is apparent that the segments shown couldbe cut from a ringshaped piece of material.

The segments are secured to the carrier plate in the desired position bymeans of the projection welds 18 or other suitable means as describedabove.

The resultant clutch plate is of considerably less weight than any priormetallic plate using sintered metal facing material and is constructedin such a manner as to have a cushioning or spring action both axiallyand circumferentially. The waved peripheral portion serves to giveresilience and a cushion-like action during the engagement of the plateand the spokes 11 serve to give a torsional spring action to the plate.Furthermore, the waved periphery of the plate and the slots 12 formingthe spokes 11 together with the spaced feature of'the segments serve tocause a rotating clutch plate to act as a fan and circulate air over theplate and cool it. If the plate is operated in a liquid, such as oil,the liquid will be circulated by the rotation of the plate and willserve to cool the same.

The spring portions 20 between the adjacent edges of the adjacent flatareas of the peripheral portion are each of uniform length as describedabove and serve to insure that the friction surfaces of the segments 14will receive uniform pressure and thus will wear in a uniform manner.Obviously the strength of these spring portions is controlled by theirdimensions. Thus, the spring strength of the plate or the pressurerequired to fully compress the same from the position shown in Fig. 4 tothat shown in Fig. 5 can be controlled by varying the thickness anddimensions of the carrier plate and spring portions 20 and by varyingthe number of friction segments used. By varying the distance betweenthe adjacent edges of the fiat areas as by changing the size of theseareas, the spring strength can also be varied. In the embodiment shown,these areas are of triangular shape and a pressure of about 1500 poundsis required to fully compress the plate. It is apparent that these areasmay be of other shape. For example, they may be of truncated triangularshape. It is merely essential that each area extend radially entirelyacross the peripheral portion of the plate and that adjacent edges ofadjacent areas be parallel so that the spring portion therebetween is ofuniform length.

The forming ring 35 shown in Fig. 6 could obviously be constructed inother ways. It is apparent that the peripheral portion 36 merely servesto hold the triangular areas 38 in desired position. Actually aplurality of separate triangular or truncated triangular pieces 38 couldbe used, However, the construction shown in Fig. 6 is preferable in thatit facilitates assembly of the various parts for the forming operation.

The set-up of the fixture 4G in Fig. 8 entails some distortion of theforming rings 35 during the heating operation. It is apparent from Fig.9 that the triangular portions 38 of a ring are alternatively displaced.This may be avoided by utilizing the arrangement shown in Fig. 10. Inthis modification, the carrier plates 1 are also shown as clampedbetween the heavy cast iron plates 41 and 44 and triangular areas areused to create the desired curvature. In this construction, theintermediate forming rings are provided with only six triangular, areas54, but these are of twice the thickness of the trangular areas 38 ofthe ring shown in Figs. 6 and 9. Thus, for the clutch plate shown havinga maximum compression of .040", these triangular areas would have athickness of .080". The triangular portions 56 of the top and bottomforming rings should have a thickness of one-half of this, or .040". Allof the forming rings of this modification have only six triangularportions, but it will be observed that the locating holes are soarranged that the triangular areas of adjacent rings are staggered by30. Thus, while the carrier plates in the modification of Fig. 9 are allbent parallel, the carrier plates in Fig. 10 are alternatively bent upand down. The modification of Fig. 10 has the advantage that thetriangular portions 54 and 56 of each forming ring are not bent ordistorted. This results in a somewhat longer life of the forming rings.

Although I have illustrated and described specific methods' of makingspecific clutch plates, it is apparent that the invention is not limitedto the specific methods or forms of construction illustrated, but may beembodied as well in other methods to provide other forms of constructionwithin the scope of the appended claims.

I claim:

1. The method of making a plurality of identical circular frictionclutch plates comprising the steps of stamping from sheet steel aplurality of flat annular plates each having a central portion, an outerperipheral portion, and spokes extending between the central and outerportions, forming convolutions between peripherally spaced triangularshaped fiat areas in the outer peripheral portion of each plate adjacentthe outer ends of slots between said spokes by hardening the plate byheating it to about 50 F., quenching the heated plate in oil whileclamped in a fixture to form the plate in the general shape of thedesired finished clutch plate, arranging said plurality of platesaxially in a stack alternately with substantially flat forming washermembers interposed between adjacent plates in the stack, each of saidmembers having a substantially solid outer peripheral portion of adiameter slightly greater than the outer diameter of each plate andhaving radially inwardly projecting triangular portions designed to matewith at least half of the triangular shaped flat areas of the adjacentplate, accurately aligning the triangular portions of said plates andwasher members, compressing the stack to cause said triangular portionsof the members to displace the triangular shaped flat areas of theplates axially in the stack to form accurately the desired convolutionsbetween the adjacent triangular shaped flat areas of each plate, placingthe stack in a furnace and heating it to a temperature of about 1000" F.suificient to relieve stresses in the plates while the peripheralportions of the plates are formed with said convolutions, then coolingthe stack and separating the plates and members.

2. The method of making a plurality of identical circular frictionclutch plates each comprising a fiat central area and a peripheral areahaving an unbroken outer edge and an even number of circumferentiallyspaced flat portions with adjacent portions axially staggered so thateach alternate flat portion lies in the same plane and all the flatportions comprise two sets lying in axially spaced planes, adjacent flatportions being joined by connecting portions of waved shape, saidcentral and peripheral areas being connected by spokes, said methodcomprising stamping from sheet steel a plurality of generally fiatplates each having said central and peripheral areas and spokes andhaving its peripheral area formed to aproxima-tely the desired wavedshape, hardening each plate by heating and quenching while clamped in afixture to fix the plate in said shape, then forming said connectingportions of each of the plates accurately in the desired waved shape byassembling said plates axially in a stack and interposing a deformingpressure member between the adjacent surfaces of each contiguous pair ofplates in the stack, each of said members being of circular shape andhaving a peripheral portion including circumferentially spaced areasseparated by intervening gaps and said members being arranged in thestack with said areas and gaps of axially adjacent members staggeredcircumferentially around the plates so that circumferentially adjacentconnecting portions of the peripheral area of each plate are forced intoaxially spaced planes when the stack is compressed, then compressing thestack, heating the stack to relieve stresses in the plates, and thenallowing the plates to cool with said connecting portions set in wavedshape.

References Cited in the file of this patent UNITED STATES PATENTS1,431,680 Petersen Oct. 10, 1922 1,535,191 Wemp Apr. 28, 1925 2,417,610Phillips Mar. 18, 1947 2,646,151 Wellman et al. July 21, 1953

1. THE METHOD OF MAKING A PLURALITY OF IDENTICAL CIRCULAR FRICTIONCLUTCH PLATES COMPRISING THE STEPS OF STAMPING FROM SHEET STEEL APLURALITY OF FLAT ANNULAR PLATES EACH HAVING A CENTRAL PORTION, AN OUTERPERIPHERAL PORTION, AND SPOKES EXTENDING BETWEEN THE CENTRAL AND OUTERPORTIONS, FORMING CONVOLUTIONS BETWEEN PERIPHERALLY SPACED TRIANGULARSHAPED FLAT AREAS IN THE OUTER PERIPHERAL PORTION OF EACH PLATE ADJACENTTHE OUTER ENDS OF SLOTS BETWEEN SAID SPOKES BY HARDENING THE PLATE BYHEATING IT TO ABOUT 1550*F., QUENCHING THE HEATED PLATE IN OIL WHILECLAMPED IN A FIXTURE TO FORM THE PLATE IN THE GENERAL SHAPE OF THEDESIRED FINISHED CLUTCH PLATE, ARRANGING SAID PLURALITY OF PLATESAXIALLY IN A STACK ALTERNATELY WITH SUBSTANTIALLY FLAT FORMING WASHERMEMBERS INTERPOSED BETWEEN ADJACENT PLATES IN THE STACK, EACH OF SAIDMEMBERS HAVING A SUBSTANTIALLY SOLID OUTER PERIPHERAL PORTION OF ADIAMETER SLIGHTLY GREATER THAN THE OUTER DIAMETER OF EACH PLATE ANDHAVING RADIALLY INWARDLY PROJECTING TRIANGULAR PORTIONS DESIGNED TO MATEWITH AT LEAST HALF OF THE TRIANGULAR SHAPED FLAT AREAS OF THE ADJACENTPLATE, ACCURATELY ALIGNING THE TRIANGULAR PORTIONS OF SAID PLATES ANDWASHER MEMBERS, COMPRESSING THE STACK TO CAUSE SAID TRIANGULAR PORTIONSOF THE MEMBERS TO DISPLACE THE TRIANGULAR SHAPED FLAT AREAS OF THEPLATES AXIALLY IN THE STACK TO FORM ACCURATALY THE DESIRED CONVOLUTIONSBETWEEN THE ADJACENT TRIANGULAR SHAPED FLAT AREAS OF EACH PLATE, PLACINGTHE STACK IN A FURNACE AND HEATING IT TO A TEMPERATURE OF ABOUT 1000*F.SUFFICIENT TO RELIEVE STRESSES IN THE PLATES WHILE THE PERIPHERALPORTIONS OF THE PLATES ARE FORMED WITH SAID CONVOLUTIONS, THEN COOLINGTHE STACK AND SEPARATING THE PLATES AND MEMBERS.